|Publication number||US7556140 B2|
|Application number||US 11/839,130|
|Publication date||Jul 7, 2009|
|Filing date||Aug 15, 2007|
|Priority date||Aug 31, 2006|
|Also published as||EP2059465A2, EP2059465A4, EP2059465B1, US7740126, US7740127, US7775341, US20080053792, US20090078536, US20090078538, US20090078539, WO2008027732A2, WO2008027732A3|
|Publication number||11839130, 839130, US 7556140 B2, US 7556140B2, US-B2-7556140, US7556140 B2, US7556140B2|
|Inventors||R. Todd Swinderman, Cristian Vava|
|Original Assignee||Martin Engineering Company|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (70), Non-Patent Citations (1), Referenced by (7), Classifications (5), Legal Events (2)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This application claims the benefit of U.S. Provisional Application No. 60/824,103, filed Aug. 31, 2006, and U.S. Provisional Application No. 60/885,084, filed Jan. 16, 2007.
Bulk material handling apparatus are used in connection with the storage and movement of bulk materials such as grain, sand, gravel, coal and the like. Bulk material handling apparatus include primary apparatus and secondary or accessory apparatus. Primary apparatus include conveyors, conveyor transfer points, transfer chutes, bins, silos, hoppers, associated structures and the like. Accessory apparatus include conveyor belt cleaners, air cannons, industrial vibrators, belt tracking devices and the like that are used in combination with primary bulk material handling apparatus. For example, accessory apparatus such as air cannons and industrial vibrators are used in combination with primary apparatus such as transfer points, transfer chutes, bins, silos and hoppers to facilitate and control the flow of bulk material through the primary apparatus and improve the performance of the primary apparatus. Similarly, secondary apparatus such as conveyor belt cleaners are used in combination with primary apparatus such as conveyors to improve the performance of the primary apparatus.
In some cases, such as in the combination of an industrial vibrator with a transfer chute, the accessory apparatus is adapted to create vibrations and to transfer vibrations to the primary apparatus to induce the flow of bulk material through the primary apparatus. In other cases, such as in the combination of a conveyor belt cleaner with a belt conveyor, vibration of the belt cleaner accessory apparatus with respect to the belt conveyor primary apparatus is preferably reduced or eliminated.
Conveyors include an endless belt for moving bulk materials from one location to a second location. As the bulk material is discharged from the conveyor belt, a portion of the bulk material often remains adhered to the belt. Conveyor belt cleaners having one or more scraper blades are used to scrape the adherent material from the belt and thereby clean the belt. The scraper blades of a conveyor belt cleaner are typically attached to a cross shaft that extends transversely across the width of the conveyor belt. The conveyor belt cleaner may include one or more tensioning devices that bias the scraper blades into engagement with the conveyor belt with a force that provides a scraping pressure between the scraper blade and the belt. The scraping edge of each scraper blade wears during use due to its scraping engagement with the moving conveyor belt. Tensioners move the scraper blades as the scraper blades wear to maintain the scraper blades in biased scraping engagement with the conveyor belt.
In order to obtain adequate performance from the conveyor belt cleaner, the scraper blades are biased into scraping engagement with the conveyor belt with a selected amount of force to generate a desired scraping or cleaning pressure between the scraper blade and the belt, and that the scraper blades be disposed at a selected cleaning angle with respect to the belt depending upon operating conditions. If the scraper blades are biased against the conveyor belt with an excessive amount of force, this may result in excessive wear to the scraper blades, may cause damage to the conveyor belt, and may cause the tip of the scraper blade to develop an excessively high temperature due to the friction generated between the scraper blade and the moving conveyor belt. If the scraper blades are biased against the conveyor belt with too small of a force, the scraper blades may not effectively clean the conveyor belt.
In addition, the scraper blades may vibrate or chatter against the conveyor belt, thereby potentially damaging the conveyor belt cleaner and/or the belt, and decreasing cleaning efficiency. Scraper blade chatter may be caused by unevenness of the conveyor belt, such as sagging of the belt, defects in the belt, or splices in the belt, and by frictional forces generated between the scraper blade and the moving belt. Chatter typically decreases as scraping pressure increases. Absent chatter, cleaning efficiency generally increases as scraping pressure increases up to the limit where the belt cover strength is exceeded. Thus, the cleaning angle of the scraper blades and the force at which the scraper blades engage the conveyor belt effect vibration or chatter of the scraper blades against the conveyor belt cleaner as well as the cleaning efficiency.
Moreover, every primary and secondary apparatus has a design mass and therefore a characteristic vibration frequency. The characteristic frequency is affected by rotating or moving components such as the belt, gear boxes, motors plus changes that occur over time with the apparatus such as quantity of bulk material conveyed or stored, wear and corrosion or by unwanted buildup of bulk solids in the form of fugitive materials such as carry back, spillage and dust. Changes in the characteristic frequency of an apparatus can be an indication of a change in its mechanical condition or its operating efficiency.
A bulk material handling accessory such as a conveyor belt cleaner. The bulk material handling accessory comprises a main frame adapted to be selectively rotatable about a first axis. The main frame comprises a cross shaft, a first mounting member attached to the cross shaft and a second mounting member attached to the cross shaft. The first mounting member may include one or more cradles, with each cradle including a receptacle. A pivot member is adapted to be located in the receptacle of the cradle. A scraping member is coupled to the pivot member such that the scraping member is pivotal with respect to the cross shaft about a second axis. The scraping member includes an arm and a scraper blade adapted to engage a conveyor belt. The arm of the scraping member includes a strut having a first end and a second end. The first end of the strut is adapted to be attached to the cross shaft by the pivot member. The second end of the strut includes a mounting member having a bracket, a retainer member and a slot formed between the bracket and the retainer member adapted to receive the scraper blade.
The bulk material handling apparatus also includes a damper mechanism having a first end coupled to the second mounting member of the main frame and a second end coupled to the scraping member. The damper mechanism is adapted to bias the scraper blade into engagement with the conveyor belt and to dampen vibration of the scraper blade with respect to the conveyor belt. The damper mechanism includes a damper having a first end coupled to the second mounting member and a second end coupled to the scraping member. The damper includes a piston and a housing having a fluid chamber. The piston is movable with respect to the housing in response to movement of the scraper blade. The fluid chamber includes a fluid such as magnetorheological fluid or electrorheological fluid. The viscosity of the fluid in the fluid chamber may be selectively changed to modify the damping characteristics of the damper in response to the operating conditions of the scraper blade by changing a magnetic field or an electric field that is applied to the fluid. The damping characteristics of the damper mechanism may be selectively varied to accommodate changes in operating conditions.
One or more mounting mechanisms may be attached to the main frame. Each mounting mechanism includes a linear positioning mechanism having a first linear actuator and a support bracket, and a rotational positioning mechanism including a pivot arm and a second linear actuator. The support bracket couples the first linear actuator to the cross shaft. The first linear actuator is adapted to selectively move the support bracket and the cross shaft along a generally linear translational axis. The pivot arm is attached to the cross shaft to the main frame and to the second linear actuator, such that the second linear actuator is adapted to selectively pivot the cross shaft about the first axis.
The invention described herein is illustrated by way of example and not by way of limitation in the accompanying figures. For simplicity and clarity of illustration, elements illustrated in the figures are not necessarily drawn to scale. For example, the dimensions of some elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference labels have been repeated among the figures to indicate corresponding or analogous elements.
The following description describes techniques of controlling accessories for a bulk material handling system. In the following description, numerous specific details such as logic implementations, opcodes, means to specify operands, resource partitioning/sharing/duplication implementations, types and interrelationships of system components, and logic partitioning/integration choices are set forth in order to provide a more thorough understanding of the present invention. It will be appreciated, however, by one skilled in the art that the invention may be practiced without such specific details. In other instances, control structures, gate level circuits and full software instruction sequences have not been shown in detail in order not to obscure the invention. Those of ordinary skill in the art, with the included descriptions, will be able to implement appropriate functionality without undue experimentation.
References in the specification to “one embodiment”, “an embodiment”, “an example embodiment”, etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to effect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.
Embodiments of the invention may be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the invention may also be implemented as instructions stored on a machine-readable medium, which may be read and executed by one or more processors. A machine-readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing device). For example, a machine-readable medium may include read only memory (ROM); random access memory (RAM); magnetic disk storage media; optical storage media; flash memory devices; and others.
Bulk Material Handling System
Referring now to
The bulk material handling accessory 6 aids the bulk material handling apparatus 4 in handling bulk material. For example, the bulk material handling accessory 6 may comprise cleaning blades that scrape, peel, or otherwise detach remnants of bulk material from a conveyor belt of the bulk material handling apparatus 4. In such an embodiment, the bulk material handling accessory 6 aids the bulk material handling apparatus 4 by preventing the bulk material from accumulating upon the conveyor belt of the bulk material handling apparatus 4 and potentially obstructing movement of the conveyor belt through the bulk material handling apparatus 4.
The bulk material handling accessory 6 may comprise a controller 12 with sensors 10 for determining characteristic signals that can be related to the operating characteristics of the bulk material handling accessory 6 and/or the bulk material handling apparatus 4. The sensors 10 may comprise motion sensors such as, for example, accelerometers to detect vibrations or other types of movement of the bulk material, the bulk material handling apparatus 4, the bulk material handling accessory 6, and/or a component of either the bulk material handling apparatus 4 or one of its accessories 6. Further, the sensors 10 may comprise temperature sensors such as, for example, infrared sensors to detect or measure temperature of the bulk material, the bulk material handling apparatus 4, the bulk material handling accessory 6, and/or a component of either the bulk material handling apparatus 4 or one of its accessories 6.
The controller 12 of the bulk material handling accessory 6 adjusts the operation of the bulk material handling accessory 6 based upon the signals of the sensors 10. Further, the controller 12 may receive signals from the user interface 8 and may further adjust operation of the bulk material handling accessory 6 based upon the signals received from the user interface 8.
The user interface 8 may comprise various combinations of input/output devices such as, for example, LCD displays, LED displays, CRT monitors, flat panel displays, printers, keyboards, keys, buttons, mice, and the like in order to present information to a user and receive input from a user. As depicted, the user interface 8 is coupled to the controller 12 of the bulk material handling accessory 6. The coupling may be implemented via wired and/or wireless technologies that enable the user interface 8 to be positioned remotely from the bulk material handling accessory such as, for example, an RS-232, an RS-422, or an RS-485 serial interface; an IEEE 802.3 (Ethernet) networking interface; an IEEE 802.11 (WiFi) interface; and other interconnect technologies that permit remote positioning of the user interface 8. Similarly, the coupling may be implemented via wired and/or wireless technologies that enable the user interface 8 to be positioned nearby or locally to bulk material handling accessory such as, for example, Universal Serial Bus (USB) interconnects, IEEE 1394 (FireWire) interconnects, PS/2 mouse and keyboard connectors, IEEE 802.15.1 (Bluetooth) interconnect, and other interconnect technologies that permit local positioning of the user interface 8. While the above associates certain interconnect technologies with “remote” or “local” positioning of the user interface 8, many of the above listed interconnect technologies are capable of supporting both “remote” and “local” user interfaces 40 despite being better suited for one or the other. Further, the above listed interconnect technologies are merely illustrative and some embodiments may utilize interconnect technologies not specifically listed above.
Further details of the bulk material handling system are presented below in regard to an embodiment where the bulk material handling apparatus 4 comprises a bulk material conveyor having a conveyor belt and where the bulk material handling accessory 6 comprises a conveyor belt cleaner with cleaning blades. However, one skilled in the art should appreciate that the following teachings in regard to the conveyor belt cleaner and conveyor belt embodiment are applicable to other embodiments of the bulk material handling system such as a chute with vibrator embodiments and a bin with air cannon embodiments.
Conveyor And Conveyor Belt Cleaner
The conveyor belt cleaner 80 includes a cleaner mechanism 86 and one or more mounting mechanisms 88A-B. The cleaner mechanism 86 includes a main frame 92 including a cross shaft 94 having a generally linear central longitudinal axis 96. The cross shaft 94 extends generally linearly between a first end 98 and a second end 100. The cross shaft 94 may include a single unitary member, or as shown in
The center shaft 102 may have a different cross-sectional configuration or size, such as a different width, height, wall thickness and the like, than the stub shafts 110A and B. The stub shafts 110A and B may remain a uniform size to facilitate mounting to the mounting mechanisms 88A-B, while the size of the center shaft 102 may be varied to take into account particular operating conditions such as the width of the conveyor belt and thereby the length of the center shaft 102 between the ends 104 and 106. Consequently, a smaller size center shaft 102 may be used with relatively narrow conveyor belts and a larger size center shaft 102 may be used in connection with wider conveyor belts to minimize deflection and to accommodate increased bending stresses. The connections between the stub shafts 110A-B and the center shaft 102 also enable the center shaft 102 to be removed from the stub shafts 110A and B while the stub shafts 110A-B remain mounted to the mounting mechanisms 88A-B.
As shown in
As shown in
The main frame 92 includes a lower mounting member 126, such as a bent plate, having a first end 128 connected to the wall of the center shaft 102 that includes the slot-like apertures 120 and a second end 130 located radially outwardly from the axis 96 with respect to the first end 128. The lower mounting member 126 also extends longitudinally generally parallel to the axis 96 between a first end 132 and a second end 134. The ends 132 and 134 extend outwardly slightly beyond the locations of the slot-like apertures 120. The lower mounting member 126 includes one or more mounting tabs 136 attached to the second end 130. Each mounting tab 136 includes an aperture 138 that extends through the mounting tab 136 in a direction generally parallel to the axis 196. The mounting tabs 136 are generally uniformly spaced along the length of the lower mounting member 126 between the first end 132 and the second end 134, with each mounting tab 136 in alignment with a respective aperture 118 and slot-like aperture 120. Each of the apertures 138 in the mounting tabs 136 is located generally concentrically about a generally linear axis 140 that extends through each of the apertures 138. The axis 140 is generally parallel to and spaced apart from the axis 96.
The main frame 92 also includes an upper mounting member 144 that extends between a first end 146 and a second end 148 and that is attached to the center shaft 102. The upper mounting member 144 includes a base 150 that is connected to the center shaft 102 generally diametrically from the lower mounting member 126 with respect to the axis 96. The base 150 includes two outwardly extending legs 152 that are generally transverse to one another such that each leg 152 is adapted to be attached to a respective wall of the tube that forms the center shaft 102. The base 150 also includes a stem 154 that extends outwardly from the junction of the legs 152. The base 150 is thereby generally Y-shaped. The stem 154 is offset at an angle with respect to the legs 152 such that the stem 154 is not disposed at an angle midway between the legs 152.
A plurality of cradles 156 are attached to the outer end of the stem 154 and are generally equidistantly spaced apart from one another along the length of the stem 154 between the first end 146 and the second end 148 of the upper mounting member 144. Each cradle 156 extends generally parallel to the base 150 between a first end 158 and a second end 160. Each cradle 156 includes an open-top and open-end receptacle 162 formed by a generally semi-cylindrical interior wall 164. Each cradle 156 also includes a pair of spaced apart and generally parallel flanges 166 that extend from the first end 158 to the second end 160. The top surfaces of the flanges 166 are generally planar and generally coplanar with one another. Each flange 166 includes one or more apertures extending therethrough. The semi-cylindrical wall 164 of the cradle 156 is formed about a generally linear axis 168. As shown in
An end cap 172, as shown in
A center cap 180, as shown in
The cleaner mechanism 86 includes one or more pivot shafts 190. Each pivot shaft 190 extends between and is rotatably mounted to adjacent pairs of cradles 156 of the upper mounting member 144. The pivot shaft 190 is generally cylindrical and extends concentrically about and along the axis 168 from a first end 192 to a second end 194. The pivot shaft 190 includes a generally cylindrical surface 196. The pivot shaft 190 is preferably made from a corrosion resistant material and may be made from metal such as stainless steel.
Each end 192 and 194 of the pivot shaft 190 is adapted to be rotatably mounted to a respective cradle 156 by a bushing 200. The bushing 200 as shown in
The sleeve 202 of each bushing 200 is adapted to be located within the receptacle 162 of a cradle 156 and is removably retained therein by clamping engagement with the end cap 172 or center cap 180. The collar 204 of the bushing 200 is positioned adjacent the end of the receptacle 162. The first end 192 of a pivot shaft 190 extends into the bore 206 of a bushing 200 located in a first cradle 156, and the second end 194 of the pivot shaft 190 extends into the bore 206 of a bushing 200 located in an adjacent cradle 156. The pivot shaft 190 thereby extends between a pair of adjacent cradles 156. The pivot shaft 190 is adapted to pivot or rotate about the central axis 168 with respect to the bushings 200 and cradle 156.
The cleaner mechanism 86 also includes one or more scraping members 210. Each scraping member 210 includes an arm 212 and a scraper blade 214. The arm 212 extends between a first end 216 and a second end 218 along a central longitudinal axis 220. The first end 216 includes a generally cylindrical hub 222 that extends generally transversely to the axis 220 between a first end 224 and a second end 226. A generally cylindrical bore 228 extends through the hub 222 from the first end 224 to the second end 226 along and concentrically about the axis 168. The pivot shaft 190 extends through the bore 228 of the hub 222 such that the first end 192 and second end 194 of the pivot shaft 190 each extend outwardly beyond the ends 224 and 226 of the hub 222 approximately an equal distance. The generally cylindrical surface of the hub 222 formed by the bore 228 is sized to closely engage the surface 196 of the pivot shaft 190. The hub 222 may be coupled to the pivot shaft 190 such that the arm 212 and pivot shaft 190 conjointly pivot with one another about the axis 168. The shaft 190 may be coupled to the hub 222 by a friction fit therebetween or by a coupling member, such as a key or weld. The pivot shaft 190 may also be integrally formed with the arm 212. Alternatively, the arm 212 may pivot with respect to the pivot shaft 190 about the axis 168.
The arm 212 includes a strut 230 having a first end coupled to the hub 222 and a second end coupled to a mounting member 232 that is located at the second 218 of the arm 212. As viewed in plan, as shown in
The mounting member 232 of the arm 212 includes a bracket 258 having a base attached to the second end of the strut 230. The bracket 258 extends upwardly from the base to a tip 260. The bracket 258 includes an interior surface 262 and a spaced apart exterior surface 264. The interior and exterior surfaces 262 and 264 are generally planar. The interior surface 262 is located in a plane that is generally parallel to the axis 168. The interior surface 264 is located more closely adjacent to the first end 216 of the arm than the exterior surface 264. One or more apertures 266 extend through the bracket 258 from the interior surface 262 to the exterior surface 264.
The mounting member 232 also includes a retainer member 270, such as an upwardly extending finger or ledge, that extends upwardly from the second end of the strut 230. The retainer member 270 is located inwardly from the bracket 258, more closely toward the first end 216 of the arm 212 than the bracket 258. The retainer member 270 extends upwardly to a distal tip 272. A transverse slot 274 extends through the mounting member 232 between the bracket 258 and the retainer member 270. The slot 274 is open at its top end between the tip 272 of the retainer member 270 and the bracket 258, and at each end. The slot 272 forms an interior wall on the retainer member 270 that is generally planar and parallel to the interior surface 262 of the bracket 258. The slot 274 also forms a bottom wall 276 that may be generally semi-circular as shown in
The scraper blade 214 of the scraping member 210 is adapted to be removably connected to the mounting member 232 of the arm 212. Alternatively, the scraper blade 214 may be integrally formed with the arm 212. As shown in
The scraper blade 214 has a thickness such that the base 280 is adapted to fit closely within the slot 274 of the mounting member 232 of the arm 212 with the interior surface 288 of the base 280 located closely adjacent the interior surface of the retainer member 270 and the exterior surface 290 located closely adjacent to the interior surface 262 of the bracket 258. The bottom end 282 of the base 280 may be curved in the form of a semi-circle to matingly engage the bottom wall 276 of the slot 274 in the mounting member 232. Alternatively, the bottom end 282 of the base 280 may be generally planar, and the bottom wall 276 of the slot 274 may be planar, for mating engagement. The scraping edge 286 of the scraper blade 214 may be rounded in the general shape of a semi-circle as shown in
The fasteners that connect the scraper blade 214 to the mounting member 232 prevent transverse movement of the scraper blade 214 with respect to the bracket 258. Frictional scraping forces applied to the scraping edge 286 of the scraper blade 214 from engagement with the moving conveyor belt 82 are resisted at least in part by engagement of the base 280 of the scraper blade 214 with the retainer member 270 of the mounting member 232. A frictional scraping force applied to the scraping edge 286 by the moving belt 82 presses the exterior surface 290 of the scraper blade 214 into engagement with the tip 260 of the bracket 258, and will attempt to pivot the bottom end 282 of the scraper blade 214 away from the interior surface 262 of the bracket 258, such that the scraper blade 214 would pivot about the tip 260 of the bracket 258. However, this pivotal movement of the scraper blade 214 is prevented by engagement of the base 280 of the scraper blade 214 with the interior surface 288 of the retainer member 270 of the mounting member 232. The scraper blade 214 may be formed from metal, such as stainless steel, and may include wear-resistant materials at the scraping edge 286 such as tungsten carbide or ceramic materials.
The cleaner mechanism 86 also includes one or more damper mechanisms 302. Each damper mechanism 302 is associated with a respective scraping member 210. The damper mechanism 302 includes a first end 303 and a second end 305. Each damper mechanism 302 includes a damper 304 and may include a sensor enclosure or box 306. As shown in
A mounting tab 320 is attached to the top of the housing 308 at the second end 305 of the damper mechanism 302. The mounting tab 320 includes a bore 322 that extends therethrough along a central linear pivot axis 324. The mounting tab 320 has a width between opposing side walls at each end of the bore 322 that enables the mounting tab 320 to be inserted between the ribs 244A-B of the arm 212, with the bore 322 in coaxial alignment with a respective pair of apertures 248A-B in each of the ribs 244A-B. A fastener, such as a bolt and nut, extends through the apertures 248 and bore 322 to thereby pivotally connect the damper mechanism 302 to the arm 212 such that the damper mechanism 302 and arm 212 are pivotal with respect to one another about the pivot axis 324. The housing 308 also includes a mounting member 326 on the opposite side of the housing 308 from the mounting member 320. The mounting member 326 includes a threaded bore 328 that extends along a generally linear axis 330 and that is in communication with the chambers 310.
The damper 304, as shown in
A diaphragm 350 is located within the housing 338 and separates the fluid chamber 340 from an accumulator chamber 352 located at the second end 334 of the housing 338. The accumulator chamber 352 may include a pressurized gas, such as nitrogen. The fluid chamber 340 includes an MR fluid, such as a fluid consisting of carbonyl iron particles suspended in silicone oil. The damper 304 includes a piston 354 having a piston head 355 located within the fluid chamber 340 and that includes a first side 356 and a second side 358. The piston head 355 divides the fluid chamber 340 into sub-chambers respectively located on each side of the piston head 355. The piston head 355 includes one or more fluid passages 360 that extend through the piston head 355 between the first and second sides 356 and 358 which place the sub-chambers of the fluid chamber 340 in fluid communication with one another. Fluid passages may also be formed between the edge of the piston head 355 and the internal side wall of the housing 338 if desired. The piston 354 includes an electrical coil 362 wrapped around the piston head 355. The piston head 355 is made of a magnetically permeable material.
The piston 354 includes a generally tubular shaft 364 having a first end 366 connected to the piston head 355 and a second end 368 that is threaded and located externally of the housing 308. The second end 368 of the shaft 364 is adapted to be inserted into the threaded bore 328 for rigid connection to the mounting member 326 of the control box 306. The shaft 364 extends concentrically about and along a linear axis 330. The shaft 364 extends through the second end 344 of the housing 338 and is sealed fluid tight thereto with a seal 370. Electrical wires extend from the electrical coil 362 through the central bore within the shaft 364 and outwardly from the second end 368, through the bore 328 and into chamber 310 of the box 306 for connection to an auxiliary controller 305.
The piston 354 is linearly slideable along the axis 330 with respect to the housing 338 in each direction along the axis 330. As the piston 354 moves along the axis 330 with respect to the housing 338 MR fluid will flow from a first sub-chamber to a second sub-chamber through the fluid passages 360 to thereby allow sliding movement of the piston 354 with respect to the housing 338. The accumulator 352 accommodates MR fluid displaced by the insertion of the shaft 364 into the fluid chamber 340 and thermal expansion of the MR fluid. Selected variation in the magnetic flux generated by the electrical coil 362 provides a corresponding change in the flow characteristics of the MR fluid. MR fluids are able to change stiffness or viscosity over a very large range. Controlling the flow characteristics of the MR fluid thereby provides control over the ability of the piston 354 to move along the axis 330 with respect to the housing 338 and to thereby dampen vibrations resulting from vibratory forces applied to the piston 354. Kinetic energy from the moving conveyor belt 82 is transferred to the damper 304 through the scraping member 210. The MR fluid in the damper converts the kinetic energy into heat and transfers the heat to the atmosphere. The damper 304 provides a relatively constant transfer of axial force between the first end 334 and second end 336 regardless of the displacement of the piston 354 with respect to the housing 338, and while dampening vibration of the scraper blade 214 with respect to the belt 82. While the control box 306 is shown in the drawings as connecting the second end 368 of the piston 354 to the arm 212, if desired, the second end 368 of the piston 354 may be pivotally connected directly to the arm 212.
The scraping force with which each scraper blade 214 is biased into engagement with the conveyor belt 82 is provided by the damper 304. Different pressures of the gas in the accumulator chamber 352, and different volumes of the accumulator chamber 352, will provide different force versus displacement output curves. A damper 304 with a large accumulator chamber 352 volume and a short piston stroke is preferred such that the output force versus displacement curve is relatively flat, whereby a relatively constant scraping force and cleaning pressure is provided between the scraper blade 214 and the belt 82. Different types of dampers 304, with different gas pressures and/or different accumulator chamber volumes, can be used as desired to provide a desired scraping force and scraping pressure. The different types of dampers 304 can be exchanged with one another in the cleaner mechanism 86 to selectively change the scraping force with which the scraper blades 214 engage the belt 82.
As stated above, the dampers 304 comprise magnetorheological (MR) fluid dampers that contain MR fluid. The MR fluid has a viscosity that is dependent upon a magnetic field, thus the dampening effect of the MR damper may be adjusted by adjusting the magnetic field applied to the MR fluid. In another embodiment, the dampers 304 comprise electrorheological (ER) dampers that contain ER fluid. Similar to the MR fluid, the ER fluid has a viscosity that is dependent upon an electric field, thus the dampening effect of the ER damper may be adjusted by adjusting the electric field applied to the ER fluid. While some embodiments utilize MR fluid dampers or ER fluid dampers, those skilled in the art should appreciate that the dampers 304 may comprise other types of controlled dampers to achieve the desired controlled dampening effect. If desired the damper 304 may include a resilient biasing member, such as a mechanical coil spring, that extends around the housing 338 and piston 354 with a first end of the biasing member coupled to the housing 338 and a second end coupled to the piston 354.
The lugs 252A and B of the arm 212 are adapted to engage the stem 154 of the upper mounting member 144 to limit pivotal movement of the arm 212 about the pivot axis 168. The lugs 252A-B thereby limit the possible length of stroke of the piston 354 of the damper 304, preventing over-retraction of the piston 354 which could damage the diaphragm 350 and preventing over-extension of the piston 354 which could damage the seal 370.
The upper mounting member 144 is designed so that the scraper blades 214 can be either in-line, or offset and overlapping. As shown in
When the scraping members 210 are configured in an offset and overlapping arrangement, the scraper blade 214 of each scraping member 210 may be pivotally mounted to the mounting member 232, such as by a single fastener extending through an aperture 226 and an aperture 296, such that the scraper blade 214 is pivotal with respect to the arm 212 about a pivot axis that is generally transverse to the axis 168. The bottom end 282 of the blade 214 is spaced apart from the bottom wall 276 of the slot 274 in the retainer member 270 when the blade 214 is in a centered position, such that the blade 214 can pivot in either direction about the pivot axis such as, for example, plus or minus five degrees before the base 280 of the blade 214 engages the bottom wall 276 of the slot 274. In this configuration, a wear-in tip should additionally be provided at the corners formed by the scraping edge 286 and the ends 292 and 294 of the blade 214 to prevent gouging of the belt 82 as the blade 214 adapts to the belt surface 84.
The cleaner mechanism 86 also includes a deflector shroud 374. As shown in
As shown in
The mounting mechanisms 88A-B may be constructed generally as mirror-images of one another. The mounting mechanism 88B is shown in
The linear positioning mechanism 394 also includes a support bracket 410. The support bracket 410 includes a generally linear bore 412 that extends from the bottom end to the top end of the support bracket 410 and that is adapted to receive the threaded shaft 400. The support bracket 410 also includes a passageway 414 that extends generally horizontally and transversely to the bore 412 through the support bracket 410 between opposite side walls. The passageway 414 includes a generally circular and concave receptacle 416 that is adapted to receive a generally circular bushing 418. The bushing 418 includes a generally circular and convex outer wall 420 that is adapted to rotatably engage and mate with the receptacle 416. The bushing 418 also includes a central bore 422 that is adapted to receive and matingly engage a stub shaft 110A or B of the main frame 92 such that the main frame 92 and the bushing 418 are conjointly rotatable about the axis 96 with respect to the support bracket 410. The support brackets 410 of the mounting mechanisms 88A-B respectively receive and support the opposing ends of the main frame 92 within the bushings 418. The support brackets 410 and the cleaner mechanism 86 are selectively moveable in a generally linear direction along the axis 402 of the shafts 400 in either direction, upwardly or downwardly, by appropriate lifting or lowering of the threaded shafts 400 about their respective axes 402 by means of nuts 456. If desired electrically operated rotational actuators may be operatively coupled to each shaft 400 to provide selected rotation of the shafts 400 and thereby selective positioning of the cleaner mechanism 86. Shaft 401 may be keyed to bore 412 to limit horizontal shifting of the assembly 80 relative to the cross axis of conveyor belt 82.
One or both mounting mechanisms 88A-B may include a rotational positioning mechanism 428. The rotational positioning mechanism 428 includes a collar 430, such as a generally planar plate, including a central aperture 432 adapted to matingly receive a stub shaft 110A or B such that the collar 430 and the main frame 92 are conjointly rotatable with one another about the axis 96. The collar 430 also includes a plurality of peripheral apertures and arcuate slots 434. The rotational positioning mechanism 428 also includes a pivot arm 436. The first end 438 of the pivot arm 436 includes a generally circular central aperture 442 adapted to receive the stub shaft 110A or B of the main frame 92. The first end 438 also includes a plurality of peripheral apertures 444 spaced in a generally uniform manner about the central aperture 442. The first end 438 of the pivot arm 436 is adapted to be removably connected to the collar 430 by fasteners that respectively extend through the peripheral apertures 434 and 444. The position of the pivot arm 436 with respect to the collar 430 about the axis 96 may be adjusted by selectively placing the fasteners within the slotted apertures 434 of the collar 430. The second end 440 of the pivot arm 436 includes an aperture 446 that is spaced apart from the central aperture 442.
The rotational positioning mechanism 428 also includes a support bracket 450 having a bore 452 adapted to threadably receive the threaded shaft 400 such that the support bracket 450 is located on shaft 402 by means of nuts 456 and supported by the shaft 400. The support bracket 450 also includes a longitudinal threaded bore 452 extending inwardly into the support bracket 450 generally transversely to the central axis of the threaded bore 452. The support bracket 450 is threadably attached to the threaded shaft 400 spaced apart from and below the bottom of the support bracket 410 of the linear positioning mechanism 394. The central axis of the threaded bore 454 extends generally perpendicular to the axis 402. One or more locking nuts 456 are threadably engaged to the shaft 400 and are located above and below the support bracket 410 and the support bracket 450 to selectively lock the brackets in place with respect to the threaded shaft 400.
The rotational positioning mechanism 428 also includes a linear actuator mechanism 460. The linear actuator mechanism 460 includes a fluid cylinder 462 having a first end 464 and a second end 466. The fluid cylinder 462 includes a housing 468 having an aperture 470 at the second end 466. The aperture 470 extends along a generally linear axis 472. An extendable and retractable linear ram 474 extends outwardly from the first end of the housing 468 to a distal end 476 having an aperture 478. The aperture 478 extends along an axis 480 that is parallel to and spaced apart from the axis 472. The ram 474 extends along a central longitudinal axis 482 that extends from the first end 464 to the second end 466 of the fluid cylinder 462. The longitudinal axis 482 is perpendicular to the axes 472 and 480.
The second end 466 of the fluid cylinder 462 is pivotally attached to the support bracket 450 by a fastener that extends through the aperture 470 and into the threaded bore 454 of the support bracket 450. The fluid cylinder 464 is thereby pivotal with respect to the support bracket 450 about the axis 474. The first end 464 of the fluid cylinder 462, and thereby the distal end 476 of the ram 474, is pivotally attached to the second end 440 of the pivot arm 436 by a fastener that extends through the aperture 478 and the aperture 446. The fluid cylinder 462 is thereby pivotal with respect to the pivot arm 436 about the axis 480. The distal end 476 of the ram 474 may be selectively moved in either direction, extended or retracted, with respect to the housing 462 along the axis 482 with respect to the housing 462.
The linear actuator mechanism 460 also includes an electrical motor operatively connected to a fluid pump 484 that is in fluid communication with the fluid cylinder 462. The electrical motor is in electrical communication with the auxiliary controllers 305 in the control boxes 306. The fluid pump 484 provides for the selective extension and retraction of the ram 474. The fluid cylinder 462 and fluid pump 484 may be hydraulically operated, or if desired may be pneumatically operated. The linear actuator mechanism 460 may be operated on direct current (DC) voltage, such as at twenty-four volts DC. The linear actuator mechanism 460 may be the Mini Motion Package actuator as manufactured by KYB Corporation.
As viewed in
As shown in
The cleaning angle of the cleaner mechanism 86 can be varied as desired between the aforementioned cleaning angles by changing the mounting distance between the rotational axis 96 of the main frame 92 and the surface 84 of the conveyor belt 82. Appropriate rotation of the shafts 400 of the mounting mechanisms 88A-B move the pivot axis 96 of the cleaner mechanism 86 along a plane 488 that is generally parallel to the central axes 402 of the shafts 400 toward the surface of the conveyor belt 82. When the shafts 400 are rotated in an opposite direction, the pivot axis 96 of the cleaner mechanism 86 will move along the plane 488 in an opposite direction away from the surface of the conveyor belt 82. The linear positioning mechanism 394 thereby allows selective placement of the pivot axis 96 of the cleaner mechanism 86 along the plane 488, such that the scraper blades 214 engage the surface 84 of the conveyor belt 82 at a desired cleaning angle, such as anywhere between a positive rake cleaning angle of forty-five degrees to a negative rake cleaning angle of minus ten degrees. Other ranges of cleaning angles may be used as desired. The cleaning angle of the scraper blades 214 can be adjusted after installation of the conveyor belt cleaner 80 to fine tune the cleaning angle to an optimal cleaning angle, and to change the cleaning angle as may be needed due to changes in belt speed, changes in the conveyed material, or changes in other operational parameters. Such adjustment can be done manually or automatically.
Once the cleaner mechanism 86 is located in its desired mounting position along the plane 488, the linear actuator mechanism 460 of the rotational positioning mechanism 48 rotates the cleaner mechanism 86 about the axis 96. Extension of the ram 474 of the fluid cylinder 462 will pivot the pivot arm 436 and the cleaner mechanism 86 in a counter-clockwise direction, as viewed in
Retraction of the ram 474 of the fluid cylinder 462 will pivot the pivot arm 436 and cleaner mechanism 86 in a clockwise direction as viewed in
Each damper 304 respectively dampens vibration of its associated scraper blade 214 with respect to the conveyor belt 82 during operation. Each damper 304 is individually controlled by a respective auxiliary controller 305 in its associated box 306, such that dampening of each scraper blade 214 can be individually controlled. The dampening characteristics of each damper 304 may be varied during operation of the conveyor belt cleaner 80 to accommodate changes in operating conditions. The operating condition of the accessory bulk material handling apparatus, such as the conveyor belt cleaner 80, air cannon, or industrial vibrator, and the operating condition of the combination of these accessory apparatus with a primary bulk material handling apparatus, is determined by sensing and monitoring the vibration emitted by the combination of the accessory and primary apparatus. Changes in the emitted vibration are used to initiate control of the accessory apparatus, such that the combination of the accessory apparatus and the primary apparatus will operate at an optimum level of performance.
The geometrical arrangement of the cleaner mechanism 86 is generally illustrated in
Bulk Material Handling Controller
Referring now to
Referring now to
Each auxiliary controller 305 controls one or more aspects of the bulk material handling accessory 6. In one embodiment, each arm 212 comprises an auxiliary controller 305 that generates control signals which cause respective dampers 304 to controllably dampen vibrations of its associated arm 212. In one embodiment, the auxiliary controller 305 generates the control signal based upon signals received from its sensors such as the accelerometers 502 and the temperature sensor 504. As explained above, the dampers 304 have a controllable dampening rate that is linear with respect to the control signals received from the auxiliary controller 305. Thus, the auxiliary controllers 305 in one embodiment may increase the dampening effect of its damper 304 by increasing the current of the control signal to the damper 304 and may decrease the dampening effect of its damper 304 by decreasing the current of the control signal to the damper 304. However, other embodiments may utilize dampers 304 that have controllable dampening rates that are non-linear with respect to the received control signals, and the auxiliary controllers 305 may generate the control signals to account for the non-linear dampening rates.
A master supply block 520 is also depicted in
The master supply block 520 may further generate a status signal which may be used to provide the master controller 500 with status information. In one embodiment, the master supply block 520 may generate a status signal to inform the master controller 500 of a power failure such as, for example, the master supply block 520 receiving inadequate power from its main power source and/or the master supply block 520 providing inadequate power to components of the bulk material handling system. Moreover, the master supply block 520 may comprise an alternate power source or power reserve such as, for example, high power batteries or supercapacitors that are capable of supplying sufficient power for the bulk material handling controller 12 and bulk material handling accessory 6 to execute a fail response in response to the status signal informing the master controller 500 of a failure of its main power source. For example, the power reserves of the master supply block 520 may provide sufficient power for the controller 12 and accessory 6 to safely respond to a situation wherein the main power source provides no power (e.g. black out) or insufficient power (e.g. brown out). In one embodiment, the master controller 500 may generate control signals that result in the positioning mechanisms 510 retracting the arms 212 from the belt 82 in order to prevent the arms 212 from damaging the belt 82 if the master supply block 520 is unable to supply sufficient power to operate the accessory 6.
Further details regarding cable connections between components of the bulk material handling controller 12 and components of a bulk material handling accessory such as the belt cleaner mechanism 86 are depicted in
The memory 542 stores data for the master controller 500. In particular, the processor 540 may read data from the memory 542 and write data to the memory 542. In one embodiment, the memory 542 comprises a removable memory card having a capacity of at least 512 kilobytes. In such an embodiment, the memory card may be removed in order to archive its stored data for future reference and/or may be removed for analysis by another computing device.
The one or more I/O interfaces 544 provide the processor 540 with interfaces for exchanging data with external devices such as the user interface 8, the auxiliary controllers 305, and the positioning mechanisms 510. In one embodiment, the auxiliary interface 544 comprises an RS-485 serial interface which couples the master controller 500 to the auxiliary controllers 305 in a daisy chain manner. The auxiliary interface 305 may further comprise other wired and/or wireless interface that may be used to operatively couple the user interface 8, the auxiliary controllers 305, and the positioning mechanisms 510 to the master controller 500. Such wired and/or wireless interfaces may include but are not limited to the following: RS-232, RS-422, RS-485 and Controller Area Network (CAN) serial interfaces; IEEE 802.3 (Ethernet) networking interfaces; IEEE 802.11 (WiFi) interfaces; Universal Serial Bus (USB) interfaces; IEEE 1394 (FireWire) interfaces; PS/2 mouse and keyboard interfaces; and IEEE 802.15.1 (Bluetooth) interfaces.
The real time clock 546 provides the processor 540 with a current time reference. The processor 540 may utilize the current time reference to time stamp data received from devices coupled to the I/O interfaces 544. The processor 540 may further utilize the real time clock 546 to synchronize operation of the master controller 500 with other components of the bulk material handling system. In one embodiment, the real time clock 546 comprises a M41T0M6 real time clock chip from ST Microelectronics.
The movement sensors 552 are generally operable to detect movement of the auxiliary controller 305, the bulk material handling apparatus 4, the bulk material handling accessory 6, the bulk material, and/or a component of the apparatus 4 or the accessory 6. To this end, the movement sensor 552 may comprise sensors that detect changes in displacement, changes in velocity, changes in acceleration, and/or other indications of movement. In one embodiment, the movement sensor 552 comprise a plurality of accelerometers where one accelerometer measures acceleration of the arm 212 and another accelerometer measures gradient or tilt of the arm 212.
The accelerometers of one embodiment have a very small size, extended temperature range (operating range −55 . . . +125° C., with guaranteed specifications at least in the −40 . . . +100° C. range), and the capability of withstanding shocks of at least 2000 g. In particular, the accelerometers may comprise MEMS (Micro Electro Mechanical System) type which typically are very small size and are capable of generating gradient information with only a simple low pass filter. In one embodiment, the accelerometers for measuring acceleration comprise the ADXL78 accelerometer, and the accelerometers used for measuring the tilt comprise the ADXL322 accelerometer both made by Analog Devices. Furthermore, in one embodiment, the accelerometers are placed on the same printed circuit board as the processor 558 and near analog inputs of the processor 558. Furthermore, the accelerometers are placed away from pulse width modulation outputs of the processor 558 to reduce electric noise that may corrupt the accelerometers signal.
The temperature sensor 554 generates an analog measurement signal that is representative of temperature sensed by the temperature sensor 554. In an embodiment, the temperature sensor 554 has a measurement range of −40° C. to +125° C. Furthermore, the temperature sensor in one embodiment comprises an AD7416ARM temperature sensor from Analog Devices although other sensors may be used.
The signal interfaces 556 may receive measurement signals from the sensors 552, 554 and condition such signals such that they are in a form suitable for inputs of the processor 558. Assuming the sensors 552, 554 generate analog measurement signals that are to be supplied to analog inputs of the processor 558, the signal interface 556 may filter, amplify, attenuate or otherwise adjust such measurement signals such that conditioned measurement signals remain within an operating range of the analog inputs of the processor 558. Similarly, if the analog measurement signals are to be supplied to digital inputs of the processor 558, the signal interfaces 556 may filter, amplify, attenuate, digitize or otherwise adjust the measurement signals such that the digitized values of the measurement signals remain within an input range of the processor 558. Likewise, the signal interfaces 556 may condition control signals generated by the processor 558 such that such control signals remain within operating ranges of those components receiving the control signals. Again, such conditioning may encompass filtering, amplifying, attenuating, and/or digitizing such control signals.
The processor 558 receives the conditioned measurement signals from the sensors 552, 554 and provides an output control signal to its respective damper 304 via a signal interface 556. In one embodiment, the processor 558 comprises either TMS320LF2401 or TMS320F2801 digital signal processor from Texas Instruments although other digital signal processors, general purpose processors, and/or microcontrollers may be used. The processor 558 in one embodiment comprises a data acquisition block 560, a digital filter 562, integrators 564, 566, a peak converter 568, an average converter 570, and root mean square (RMS) converter 572, a signal selector 576, a proportional-integral-derivative (PID) controller 578, and a pulse width modulation (PWM) controller 578. One skilled in the art should appreciate that many of the functional components of the processor 558 may be implemented as specialized hardware circuitry and/or software executed by general purpose circuitry.
The data acquisition block 560 receives conditioned measurement signals from the sensors 552, 554 via the signal interfaces 556 and converts such analog signals into digital samples that are representative of the received signals. In one embodiment, the data acquisition block 552, 554 receives measurement signals from two accelerometers 552 and thus generates two digitized signals therefrom. One digitized signal is representative of acceleration of the arm 212 and the other digitized signal is representative of the tilt or gradient of the arm 212.
The digital filter 562 receives the digital signals from the data acquisition block 560 and further filters the digital signal to remove the noise and limit the digital signal to an particular bandwidth. In one embodiment, the digital filter 562 is implemented with a low group delay that is relatively constant within the operational bandwidth of 0 to 250 Hz. In particular, one embodiment of the digital filter 562 is implemented using a Remez exchange algorithm technique in order to reduce control error resulting from delay introduced by the digital filter 562 and other components of the auxiliary controller 305. In one embodiment, the maximum delay in the processing chain including the filter 562 is 13.7 us in order to maintain control error introduced by control delay at an acceptable level.
The first integrator 564 in one embodiment receives a digital signal from the digital filter 562 that is representative of acceleration of the arm 212 and integrates the signal to obtain a digital signal that is representative of velocity of the arm 212. Similarly, the second integrator 566 in one embodiment receives a digital signal from the first integrator 564 that is representative of velocity and integrates the signal to obtain a digital signal that is representative of displacement of the arm 212. The peak converter 568, average converter 570, and the RMS converter 572 each receives the digital signals from the digital filter 562 and the integrators 564, 566 and generates output signals that respectively represent the peak values, average values and RMS values of the received signals during an analysis period. In one embodiment, the analysis period is set to 0.5 seconds. However, the peak converter 568, average converter 570 and RMS converter 572 in one embodiment may be programmed with an analysis period between the range of 50 microseconds to over 3 seconds.
The signal selector 574 receives the digital signals from the digital filter 562, the integrators 564, 566, and the converters 568. 570, 572 and selects signals of interest for the PID controller 576. In one embodiment, the signal selector 574 represents a function implemented by software that allows other software components of the auxiliary controller 305 to select signals for a control algorithm.
The PID controller 576 receives selected signals from the signal selector and generates a digital control signal based thereupon. In one embodiment, the PID controller 576 processes the selected signals based upon a control algorithm designed to control the bulk material handling accessory 6 in a desired manner. As will be explained below, the PID controller 576 in one embodiment generates the control signal based upon a damping control algorithm that attempts to maintain the scraper blades 214 of arms 212 in contact with belt surface 84 with an appropriate contact force which reduces chatter and scraper blade induced damage to the belt 82.
The PWM controller 578 receives the digital control signal and converts the digital control signal to an analog control signal. In particular, the PWM controller 578 generates the analog control signal with a pulse having a width that is proportional to the value of the digital control signal.
As mentioned above, the auxiliary controllers 305 control the dampening effect of the controlled dampers 304. In particular, the auxiliary controller 305 in one embodiment generates a control signal for its damper 304 based upon measurement signals that are indicative of acceleration of the arm 212. More specifically, the auxiliary controller 305 generates the control signal based upon a control algorithm that attempts to maintain proper cleaning pressure between the cleaning mechanism 86 and the conveyor belt 82, to reduce effects of shocks induced by large belt defects, and to reduce wearing effects on the belt 82, cleaning mechanism 86, and other mechanical components.
During operation of the belt cleaning mechanism 86, the belt cleaner arm 212 does not precisely follow the shape of the conveyor belt 82 due the inability of the belt cleaning mechanism 86 to react instantly to changes in the conveyor belt 82. Despite manufacturing intent, the surface 84 of the conveyor belt 82 is not completely even. The unevenness of the belt 82 results in the distance between the tips 260 of the scraper blades 214 and the belt 82 changing since belt cleaning mechanism 86 is unable to react instantly to such changes in the belt 82. The distance between the tips 260 and the belt surface 84 is further influenced by belt sag, major belt defects, and friction. Belt sags tend to induce relatively slow motion (e.g. several Hz) of belt surface 84 and the tips 260. However, major belt defects commonly induce fast motion (e.g. tens or hundreds of Hz) of the tips 260 as a result of the tips striking the major belt defects. Further, even without major belt defects, friction between the tips 260 and the belt surface 84 results in the tips 260 being pushed away from the surface 84.
The controlled dampers 304 have a dampening effect which may be represented by a damping coefficient c. In one embodiment, the damping coefficient c is linear with respect to the current of the control signal applied to the controlled dampers 304. Software of the auxiliary controllers 305 causes the processors 558 to select via the signal selector 574 from available status signals such as displacement signals, velocity signals, acceleration signals, peak signals, average signals, and RMS signals and determine the current of the control signal to apply to the dampers 304 in order to obtain a desired damping.
The status signal used by the auxiliary controllers 305 to control the dampers 304 may be one or more of the status signals applied to the signal selector 574. In the one embodiment, the auxiliary controllers 305 generate the control signals based upon the derived displacement signals. However, those skilled in the art should appreciate that one or more of the other status signals may be useful for other bulk material handling apparatus 6 or other embodiments of the belt cleaner apparatus 80. Further, it should be appreciated that since displacement signal in the present embodiment is calculated or derived from the acceleration signal, the displacement signal may not correspond to the actual displacement but rather a value proportional to the actual displacement.
Through mathematical analysis and extensive experimentation it has been determined that appropriate results are achieved when the control signal and the status signal exhibit the relationship depicted in
As shown in the examples in
In a practical installation, a technician sets the system parameters S1, S2, S3, and S4 based on experience, system physical size, belt characteristics, and conveyed material characteristics. A technician may analyze the system behavior and change the coefficients S1, S2, S3, and S4 in such a way as to improve the parameters that are the most important for that particular application at that time. For example, because of heavy rains, conveyed material may become wet and sticky. Therefore the technician may decide to temporarily increase the pressure exerted by the scraper blades 212 against the belt surface 84. To achieve this goal, the technician may increase the minimum value C1 thus increasing the minimum value of the control signal.
Additionally, the control signal plots need not be symmetrical. In some instances, asymmetrical control signal patterns may prove to be useful. The reason for this behavior is that if the right side has a more shallow slope then the mechanical energy absorbed from the external force is lower since the coupling factor is lower. If the left side has a steeper slope the mechanical energy dispersed to the environment is higher since the coupling factor is higher. In one embodiment, the manufacturer and later on the technician may choose the control parameters C1, C2, S1, S2, S3, S4 with the goal of reducing the spectral components in the displacement error. By transferring a signal from the time domain to the frequency domain (Fourier Transform) the energy content is preserved. This is a direct consequence of the Wiener Khintchine theorem (the power spectral density of a wide-sense-stationary random process is the Fourier Transform of the corresponding autocorrelation function). Therefore by analyzing the displacement error spectrum in the frequency domain, it is possible to select parameters that reduce the error. To permit this selection of parameters, the bulk material handling controller 12 may collect data and may execute the configuration algorithm described below to determine the control parameters for reduced displacement error.
Configuration of Damping Control
The auxiliary controller 305 in block 606 calculates a cost value from the collected data which provides a measure of the effectiveness of the bulk material handling controller 12 when operating based upon the selected system parameters C1, C2, S1, S2, S3, and S4. In one embodiment, the auxiliary controller 305 for each displacement error x(t) computes its discrete Fast Fourier Transform (FFT) fx[i] where i is the harmonic order. Then, the auxiliary controller 305 computes for each fx(i) set the cost function defined as the root means square contribution:
where n represents the number of relevant harmonics found in fx[i]. In one embodiment, the number of relevant harmonics is 55 times the excitation frequency. However, for ease of calculation in a small embedded system n=64 being the smallest power of 2 that is larger than 55.
In one embodiment, the auxiliary controller 305 attempts to select the system parameters C1, C2, S1, S2, S3, and S4 such that overall displacement error is reduced in order to maintain the scraper blades 214 appropriately biased against the surface 84 of the conveyor belt 82. However, it is possible to design other configuration methods that attempt to reduce the response time or the overshoot, thus configuring the auxiliary controllers 305 to account for other aspects that may be more important to operation of certain types of bulk material handling accessories 6. For example, if the goal of the configuration method is to reduce the overshoot, the cost function may be replaced with a new cost function defined as:
R x=max(|x[i]|)i=0 . . . n,
where max( ) is a function extracting the maximum from the list of absolute values of the displacement error x.
The auxiliary controller 305 then records in block 608 the calculated cost value and associated set of selected parameters C1, C2, S1, S2, S3, and S4. The auxiliary controller 305 then in block 610 decides whether to perform another configuration cycle. In one embodiment, the auxiliary controller 305 iterates through possible values for the system parameters C1, C2, S1, S2, S3, and S4 and elects to repeat another configuration cycle if further possible values remain. In another embodiment, the auxiliary controller 305 iterates through possible values until either a specified cost value is satisfied or until all values have been tested. For example, the auxiliary controller 305 may be configured to stop once a set of parameters results in an error (cost) below a defined threshold amount.
In block 612, the auxiliary controller 305 selects a set of parameters C1, C2, S1, S2, S3, and S4 based upon their associated cost values Rx[i]. In one embodiment, the auxiliary controller 305 attempts to minimize the cost or displacement error x(t) and as such selects the set of parameters C1, C2, S1, S2, S3, and S4 associated with the smallest cost Rx[i]. However, it should be appreciated that for other cost functions or other embodiments the auxiliary controller 305 may attempt to maximize the cost value for some aspect of the bulk material handling accessory 6. In such an embodiment, the auxiliary controller 305 then may select the set of parameters C1, C2, S1, S2, S3, and S4 associated with the largest cost value.
While the auxiliary controllers 305 may execute the method of
By running the configuration method in a simulation environment such as the SciLab, Octave, or Matlab, it has been determined that for the mechanical parameters used in the simulations, the control parameters of C2=Cmax, C1=Cmin, S1=S2−1 mm, S3=5 mm, S4=10 mm provide appropriate results for one embodiment of the belt cleaner 80. As a result, these values are used as a default control set in one embodiment.
A safety management method which may be executed by the master controller 500 is depicted in
The master controller 500 then in block 632 may determine whether the movement of the arm 212 is acceptable or whether some protective action is to be taken in order to maintain safety. The following description is in regard to making a determination based upon received acceleration status signals. However, it should be appreciated that a similar scheme may be used to make such a determination based upon velocity, displacement, peak, average and/or RMS status signals. In one embodiment, the master controller 500 basically defines three protection zones. An upper zone corresponds to acceleration values that are greater than a programmed upper threshold amax. A lower zone corresponds to acceleration values that are lower than a programmed lower threshold amin. A middle zone corresponds to acceleration values that fall between the upper threshold amax and the lower threshold amin. If the acceleration status signal indicates acceleration in the upper zone, then the master controller 500 determines to take protective action and proceeds to block 642 in order to take such action. Conversely, if the acceleration status signal indicates acceleration in the lower zone, then the master controller 500 determines not to take protective action and proceeds to block 634 in order to determine whether to take protective action based upon a temperature status signal.
For accelerations that fall in the middle protection zone, the master controller 500 triggers protective action in a delayed manner with a delay defined as:
t=k t ·e −a·k
where a represents the instantaneous acceleration, and kt and kc are predetermined coefficients. In one embodiment, the upper threshold, lower threshold, and coefficients are defined as: amax=500 m/s2; amin=250 m/s2; kt=10000; and kc=1/32. By delaying response for accelerations falling in the middle zone, the master controller 500 permits the bulk material handling accessory 6 to have short time periods of accelerations in the middle zone, but triggers protective action if accelerations above the lower threshold remain for an extended period of time.
In addition to the above three protection zones, a technician may use the user interface 8 to define limits regarding differences in acceleration, velocity, and displacement between adjacent arms 212 of the belt cleaner 80. If the master controller 500 determines that movement of adjacent arms 212 differs by an amount that exceeds the thresholds set by the technician, then the master controller 500 may determine to proceed to block 642 to take protective action. One reason the arms 212 may experience different movement is that the cleaner mechanism 86 may not be properly mounted thus resulting in the arms 212 not being properly aligned to the conveyor belt 82. Another reason is that the belt 82 may have been damaged locally resulting in one auxiliary controller 305 sustaining significantly higher shocks. Regardless of the cause, substantial differences in movement between the arms 212 is an indication of potentially unsafe operation of the belt cleaner 80, thus prompting the master controller 500 to take action.
If the movement is acceptable, then the master controller 500 in block 634 may receive temperature status signals from the auxiliary controllers 305 and may determine in block 636 whether the temperature reported by the received status signals is acceptable. In one embodiment, if the temperature reported by an auxiliary controller 305 leaves a specified range, the master controller 500 determines to proceed to block 642 to take protective action. A technician in one embodiment may use the user interface 8 to set the temperature limit according to the conveyor belt material, conveyed material, regulations, and other environment conditions. For example in potentially explosive environments, the temperature limit may be dictated by the flammability of that particular environment.
In block 638, the master controller 500 may receive status signals from the master supply block 520 and the local power supplies 550 regarding the power supply capabilities of the respective units. The master controller 500 in block 640 may determine based upon the received status signals for the power supplies whether to take protective action. In one embodiment, the master controller 500 proceeds to block 642 to take protective action if any local power supply 550 is not fully functional or the master supply block 520 fluctuates outside of some safe limits.
In block 642, the master controller 500 takes protective action. In one embodiment, the master controller 500 generates control signals which cause the positioning mechanisms 530 to retract the cleaner mechanism 86 with all arms 212 away from the belt 82. Further, the master controller 500 may inform a technician via the user interface 8 regarding the protective action taken and/or the cause of the protective action.
In addition to the above protective measures, the conveyor belt cleaner 80 in one embodiment comprises further protective features. In particular, the dampers 304 of the belt cleaner arms 212 in one embodiment are pre-biased at the minimum damping value C1. As a result, if bulk material handling controller 12 fails, the damping automatically switches to a low and safe value and stays that way until the maintenance technician restores the fully operational state. Further, pre-biasing protects the dampers 304 as such devices may be destroyed by large swings if the damper coil is left without power supply.
Activity Monitoring & Functional Data Storage (AM&FDS)
The main controller 500 in one embodiment interrogates each auxiliary controller 305 in order to obtain movement, temperature and other status data therefrom. In one embodiment, the main controller 500 periodically interrogates the auxiliary controllers 305 for such data. In another embodiment, instead of interrogating each of the auxiliary controllers 305, the auxiliary controllers 305 periodically send the master controller 500 collected status information. Regardless of how the master controller 500 obtains the data from the auxiliary controllers 305, the master controller 500 in one embodiment maintains an activity log that includes the operational values of each arm 212, time stamps such values and corresponding parameters that have been used to operate the arms 212. The corresponding parameters include the measured and derived values as described above and other values like the range of safe operation for each safety feature.
The main controller 500 may store all this information in memory 542 and makes such data available to local or remote users via the user interface 8. When the local memory 542 is full, the main controller 500 may generally remove older data to make room for newer data. However, certain data which is deemed more important such as, for example, user commands received via the user interface 8 may be kept for longer periods for legal and safety reasons.
As previously described, each auxiliary controller 305 in one embodiment has the capability of measuring or estimating through computations the following real-time values: acceleration, velocity, displacement, arm inclination (tilt), and temperature. Further, each auxiliary controller 305 is capable to compute for each measured sample of acceleration, velocity, and displacement the following values: average, peak, root mean square value. These values can be used by the master controller 500 to monitor system activity and make adjustments to the components.
The master controller 500 for example may determine the working status of each arm 212 based upon the arm inclination. In particular, the master controller 500 may interrogate each auxiliary controller 305 on a regular basis. Therefore, the master controller 500 may maintain a log of arm inclination data for each arm 212. The master controller 500 may maintain the logs such that the first arm inclination entry for each arm 212 corresponds to an arm inclination reference at the time of installation. The master controller 500 may then use the arm inclination data to measure wear of the belt 82 since as the belt 82 wears the angle or inclination of the arms 212 changes.
The master controller 500 may further monitor belt loading and/or the composition of the conveyed material based upon status signals received from the auxiliary controllers 305. In particular, the master controller 500 may monitor the displacement of each arm 212 and determine the loading of the belt 82 based upon variation of the displacement. As shown in
Various features of the invention have been particularly shown and described in connection with the illustrated embodiment of the invention, however, it must be understood that these particular arrangements merely illustrate, and that the invention is to be given its fullest interpretation.
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|U.S. Classification||198/499, 198/497|
|Oct 19, 2007||AS||Assignment|
Owner name: MARTIN ENGINEERING COMPANY, ILLINOIS
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:SWINDERMAN, R. TODD;VAVA, CRISTIAN;REEL/FRAME:019987/0678;SIGNING DATES FROM 20071017 TO 20071018
|Jan 7, 2013||FPAY||Fee payment|
Year of fee payment: 4